Among various video display systems available in the art, an optical projection system is known to be capable of providing a high quality display in a large scale. In such an image display system, light from a lamp is uniformly illuminated onto an array of actuated mirrors such that each of the mirrors is coupled with a corresponding one of the actuators. The actuators may be made of an electrodisplacive material such as a piezoelectric or an electrostrictive material which deforms in response to an electric field applied thereto.
The reflected light beam from each of the actuated mirrors is incident upon an aperture of a baffle. By applying an electrical signal to each of the actuators, the relative position of each of the mirrors to the incident light beam is altered, thereby causing a deviation in the optical path of the reflected beam from each of the actuated mirrors. As the optical path of each of the reflected beams is altered, the amount of light reflected from each of the mirrors which passes through the aperture is changed, thereby displaying an image.
Apparatus for optically modulating primary beams of light to make a color image has been known in the art. For example, U.S. Pat. No. 5,150,205, filed on Nov. 1, 1989 by Gregory Um and Andrei Szilagyi, issued on Sep. 22, 1992 and entitled "ACTUATED MIRROR OPTICAL INTENSITY MODULATION", discloses an optical intensity modulator by using the actuated mirrors. The modulator comprises a white light source having a collimation lens; a beam splitter for splitting the white light into three primary lights; a beam spreader for spreading the primary light beams; a non-reflective surface having apertures therein; a scanner for providing a horizontal sweep of the light beams onto a projection screen; a collimation lens; and a projection lens. The patent issued to Gregory Um et al. has certain deficiencies, however. For instance, there are problems associated with an inaccurate horizontal sweep caused by using the mechanically rotating scanner and an inaccurate control of reflection at the beam spreader resulting from using hinged actuated mirrors therein.
Various efforts for remedying the above problems have been made. The mechanical scanner disclosed in the U.S. Pat. No. 5,150,205 has been eliminated (see U.S. Pat. No. 5,560,697 issued on Oct. 1, 1997, and entitled "OPTICAL PROJECTION SYSTEM"). The beam splitter has been replaced with an M.times.N pixel filter (see U.S. Pat. No. 5,612,814 issued on Mar. 18, 1997 and entitled "COMPACT SIZED OPTICAL PROJECTION SYSTEM"). The hinge in the actuated mirror of the beam spreader has been eliminated and improved to have various alternatives(see U.S. Pat. No. 5,661,611 issued on Aug. 26, 1997 and entitled "THIN FILM ACTUATED MIRROR ARRAY AND METHOD FOR THE MANUFACTURE THEREOF"). The actuated mirror in the beam spreader has been further improved to have a mirror arranged on top of an actuated structure in order to overcome the inaccurate control of reflection at the beam spreader (see U.S. Pat. No. 5,760,947 issued on Jun. 2, 1998 and entitled "THIN FILM ACTUATED MIRROR ARRAY FOR USE IN AN OPTICAL PROJECTION SYSTEM AND METHOD FOR THE MANUFACTURE THEREOF"). Furthermore, a new driver circuit has been introduced to efficiently drive the actuated mirrors (see U.S. Pat. No. 5,793,348 issued on Aug. 11, 1998 and entitled "ACTUATED MIRROR ARRAY DRIVING CIRCUIT HAVING A DAC").
Each of the above-mentioned improvements, however, has been made rather independently and is limited to certain parts of the entire image display system. Further, an unavoidable heat accumulation in the system incurred by the light source may cause a malfunction or even failure of the system. Accordingly, there has continued to exist a need for a more feasible and reliable image display system.